Validation of reference evapotranspiration from Meteosat Second Generation (MSG) observations

Trigo, Isabel F.; Bruin, Henk De; Beyrich, Frank; Bosveld, Fred C.; Jiménez-Gavilán, Pablo; Groh, Jannis; López-Urrea, R.

doi:10.1016/j.agrformet.2018.05.008

Cited by 33 publications

(49 citation statements)

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“…Recent analyses of actual ET data sets revealed that LAE can yield an increase in ETo of 30%. This occurs essentially in arid regions at high temperature [4,5], i.e., under the conditions where crops need irrigation. Due to the significance of LAE matter, in this paper we will consider two cases with and without LAE, respectively.Our approach is physically based and follows from the application of thermodynamics to estimate the ET of a 'saturated' surface, combined with atmospheric boundary layer (ABL) physics; this methodology will hereafter be denoted as the T-ABL model.…”

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confidence: 99%

“…When LAE plays a role, additional sensible heat due to horizontal advection of the warm and dry adjacent fields, should be accounted for. The T-ABL model recently presented by [4,5] is physically sound with some minor empirical aspects. Theoretically, it differs from the physical reasoning behind PM-ETo, which is based on a combination of thermodynamics, a simplified description of the vegetation layer model (Monteith's 'big-leaf' model) and Monin-Obukhov's similarity theory leading to empirical flux-profile relationships.…”

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confidence: 99%

“…If one fails to apply these adjustments, ETo will be overestimated significantly [12]. The T-ABL approach requiring only R s and T, hardly suffers from surface aridity [4,5]. Water 2019, 11, 382 3 of 12Recently, [5] presented an application of the T-ABL model where R s estimates from Meteosat Second Generation (MSG) observations [13,14] combined with T weather forecasts were used to derive ETo.…”

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confidence: 99%

“…The T-ABL approach requiring only R s and T, hardly suffers from surface aridity [4,5]. Water 2019, 11, 382 3 of 12Recently, [5] presented an application of the T-ABL model where R s estimates from Meteosat Second Generation (MSG) observations [13,14] combined with T weather forecasts were used to derive ETo. The approach is used by Satellite Applications Facility on Land Surface Analysis (LSA SAF; http://lsa-saf.eumetsat.int) to operationally generate daily ETo [5].This note can be seen as an extension of [5], dealing with the practical aspects of the T-ABL model and its possible advantages for certain applications, when compared with PM-ETo.…”

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confidence: 99%

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confidence: 99%

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A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

Bruin

Trigo

2019

Water

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Reference crop evapotranspiration (ETo) plays a role in irrigation advisory being of crucial importance for water managers dealing with scarce water resources. Following the ETo definition, it can be shown that total solar radiation is the main driver, allowing ETo estimates from satellite observations. As such, the EUMETSAT LSA-SAF operationally provides ETo primarily derived from the European geostationary satellite MSG. ETo estimations following the original FAO report require several meteorological observations gathered over actual well-watered grass. Here we will consider the impact of two effects on ETo using the LSA-SAF and FAO methodologies: (i) local advection, related to the impact of advection of surrounding warm dry air onto the reference non-water stressed surface; and (ii) the so-called surface aridity error, which occurs when calculating ETo according to FAO, but with input data not collected over well-watered grass. The LSA-SAF ETo is not sensitive to any of these effects. However, it is shown that local advection may increase evapotranspiration over a limited field by up to 30%, while ignoring aridity effects leads to a great overestimation. The practical application of satellite estimates of ETo provided by the LSA-SAF are discussed here, and, furthermore, water managers are encouraged to consider its advantages and ways for improvement.

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

Bruin

Trigo

2019

Water

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Crop Evapotranspiration

Todorović¹

2019

Encyclopedia of Water

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Evapotranspiration is a process referring to water transfer from the land to the atmosphere by evaporation, from the soil surface, and by transpiration, through the vegetation. It is a complex process of great relevance for the hydrological balance at different scales. Nevertheless, it is difficult to measure and estimate; hence, almost all evapotranspiration data contains errors. The main biophysical principles of evapotranspiration are described together with the most relevant methods for measurement and estimation. Particular attention is given to crop evapotranspiration used in irrigation scheduling and agricultural water management. The estimation of crop evapotranspiration is presented following the two‐step approach based on crop coefficient and reference evapotranspiration. The concept of reference evapotranspiration is expounded by means of the Penman–Monteith approach that combines surface energy balance and aerodynamic principles of the process. The indicative data of crop coefficient and length of crop growing stages are reported in tables for most relevant agricultural crops and the world growing regions. A detailed description of calculation procedures for the estimation of reference and crop evapotranspiration is presented together with the methods to improve crop coefficient estimate under specific growing conditions. Finally, numerical examples of reference and crop evapotranspiration are given in Appendix 1.

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Evaluation of WaPOR V2 evapotranspiration products across Africa

Blatchford

Mannaerts

Njuki

et al. 2020

Hydrological Processes

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The Food and Agricultural Organization of the United Nations (FAO) portal to monitor water productivity through open‐access of remotely sensed derived data (WaPOR) offers continuous actual evapotranspiration and interception (ETIa‐WPR) data at a 10‐day basis across Africa and the Middle East from 2009 onwards at three spatial resolutions. The continental level (250 m) covers Africa and the Middle East (L1). The national level (100 m) covers 21 countries and 4 river basins (L2). The third level (30 m) covers eight irrigation areas (L3). To quantify the uncertainty of WaPOR version 2 (V2.0) ETIa‐WPR in Africa, we used a number of validation methods. We checked the physical consistency against water availability and the long‐term water balance and then verify the continental spatial and temporal trends for the major climates in Africa. We directly validated ETIa‐WPR against in situ data of 14 eddy covariance stations (EC). Finally, we checked the level consistency between the different spatial resolutions. Our findings indicate that ETIa‐WPR is performing well, but with some noticeable overestimation. The ETIa‐WPR is showing expected spatial and temporal consistency with respect to climate classes. ETIa‐WPR shows mixed results at point scale as compared to EC flux towers with an overall correlation of 0.71, and a root mean square error of 1.2 mm/day. The level consistency is very high between L1 and L2. However, the consistency between L1 and L3 varies significantly between irrigation areas. In rainfed areas, the ETIa‐WPR is overestimating at low ETIa‐WPR and underestimating when ETIa is high. In irrigated areas, ETIa‐WPR values appear to be consistently overestimating ETa. The relative soil moisture content (SMC), the input of quality layers and local advection effects were some of the identified causes. The quality assessment of ETIa‐WPR product is enhanced by combining multiple evaluation methods. Based on the results, the ETIa‐WPR dataset is of enough quality to contribute to the understanding and monitoring of local and continental water processes and water management.

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Validation of reference evapotranspiration from Meteosat Second Generation (MSG) observations

Cited by 33 publications

References 32 publications

A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

A New Method to Estimate Reference Crop Evapotranspiration from Geostationary Satellite Imagery: Practical Considerations

Crop Evapotranspiration

Evaluation of WaPOR V2 evapotranspiration products across Africa

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